Have you looked for additional content in the Content Browser? Have you installed content beyond the "Global" content, such as the US Imperial content, US Metric content or other content appropriate to your location?
If so, and that content does not have what you want, can you be more specific about what you want? If I understand correctly, a single-hung window is not necessarily very different from a double-hung, except that one of the sashes is fixed. At the level of detail typically shown in an AEC Window, the styles of double-hung content provided could be copied, and the copies renamed single-hung. If you have a specific configuration in mind, posting an image of what you want will allow others to provide more specific directions on how to achieve what you are trying to do.
I think I've seen more comprehensive windows in the UK content pack.
It's intended to use DWA's for more comprehensive windows but I like being able to insert brick sizes in the Window object so I created models of complex but common windows for Australia using mass elements and doctored window blocks and set them to stretch within. That has limitations (like the blocks stretch out of proportion) but within certain parameters is acceptable to me and very quick now for insertion because the are on a tool pallete.
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